1. Field of the Invention
The present invention relates to an engine unit of an outboard motor particularly provided with an improved structure of a magneto device.
2. Prior Art
In an outboard motor, it is common to vertically dispose a crankshaft in an engine. The crankshaft is supported in the engine by a bearing, and lubricating oil is pumped to the bearing in a certain arrangement. An oil seal is provided above the bearing so that the lubricating oil will not leak outside from the bearing which supports an upper end of the crankshaft. The oil seal is mounted to the engine using a separate seal housing in many cases.
Meanwhile, in order to absorb variation in rotation of the engine and to deal with abrupt variation in load at the time of shifting, a rotation member having great moment of inertia is provided on an axis of revolution of the engine, usually on the crankshaft.
In the case of the engine unit of the outboard motor, the upper end of the crankshaft is usually projected above the engine body in an usual state to be mounted to a hull, for example, and the rotation member having great moment of inertial, i.e., a flywheel is provided on this projected portion. The flywheel constitutes a portion of a magneto device. In this case, it is a common method to integrally form the flywheel with a rotor constituting a part of the magneto device, and to fix a stator to which an electric generating coil is mounted to the seal housing which also serves as a mounting member of the stator. A recoil starter apparatus for manually starting the engine is provided above the magneto device in some cases.
A factor which determines a height of the outside shape of the outboard motor is a structural member provided on an upper portion of the engine, which, in generally, corresponds to the above-described magneto device and the recoil starter device.
Such location is not preferable because the height of the structural member is increased and the entire outboard motor is increased in size. Further, the shape of an engine cover must be considered in accordance with the structural member, and flexibility of styling is limited.
Further, the flywheel having great mass is supported in a cantilever manner by the bearing which supports the upper end of the crankshaft. Therefore, as the projecting length of the crankshaft outside from the engine is increased, even a slight deviation in revolution balance generated by the flywheel increases vibration, and this becomes a great burden to the crankshaft and the bearing. Even slight deviation in revolution balance generated by the engine and the crankshaft applied to an end of the crankshaft functions as a great moment, and this moment becomes a great burden to the crankshaft and the bearing and also becomes a factor for increasing the vibration.
It is not preferable to increase the crankshaft and the bearing in size and to change the material and producing method in order to prevent the vibration and to enhance the durability of the respective constitutional members.
The present invention has been accomplished in view of the above circumstances, and it is an object of the invention to provide an engine unit of an outboard motor capable of making compact the engine unit in size by shortening a projecting length of a crankshaft outward of an engine with a simple structure.
This and other object can be achieved according to the present invention by providing an engine unit of an outboard motor comprising:
an engine body;
a crank case in which a crankshaft is vertically perpendicularly arranged in a usable mounted state of the outboard motor;
a cylinder block which is disposed to a rear side of the crank case and in which cylinders are arranged;
a cylinder head disposed to a rear side of the cylinder block, the crank case, the cylinder block and the cylinder head being disposed in the engine body; and
a magnet device mounted to a top end portion of the crankshaft projecting upward and comprising a stator and a flywheel to which a rotor is integrally formed,
the crankshaft being supported by a bearing boss disposed to a mating portion of the cylinder block and the crank case through a bearing means and an oil seal is disposed between the bearing boss and the bearing means, the magnet device being mounted to the engine body through the stator through a mounting portion, wherein a diameter of the mounting portion of the stator is larger than an outer diameter of the oil seal.
In a preferred embodiment, the stator is directly mounted to the engine body. The engine body is formed with a hole through which the stator is mounted and the hole has a depth deeper than a position of a mounting portion of the oil seal.
The engine unit may further comprise a crank angle detecting sensor disposed to an upper surface of the engine body and a mounting boss for mounting the sensor disposed to be deviated sideways from a center line of the cylinder of the engine, the sensor being mounted to the mounting boss in an upside-down attitude.
The engine unit may further comprise a starter motor, a mounting boss for mounting the starter motor to the engine body, and a crank angle detecting sensor which is mounted to a boss formed to the starter motor mounting boss.
The engine unit may further comprise a cam shaft driving mechanism which is disposed below the bearing means.
As explained above, in the engine unit of the outboard motor of the present invention, the crankshaft is vertically disposed in the engine (engine body), an upper end of the crankshaft is projected upward of the engine as a projection, and the projection is provided with the magneto device, a bearing boss above a bearing which supports an upper end of the crankshaft is provided with an oil seal, a diameter of a mounting portion of a stator constituting the magneto device to the engine is set greater than an outer diameter of the oil seal. Therefore, the stator can be disposed outward of the oil seal, the projecting length of the crankshaft outside of the engine is shortened, and the entire height of the engine is lowered.
Further, since the stator is directly mounted to the engine, the seal housing which was necessary in the conventional structure can be eliminated, the number of parts is reduced, the projecting length of the crankshaft outward of the engine is shortened, and the entire height of the engine is lowered.
Further, since the engine is formed with a hole for mounting the stator, and a depth of the hole is set deeper than a position of a mounting portion of the oil seal, the projecting length of the crankshaft outward of the engine is shortened, and the entire height of the engine can be reduced.
Furthermore, the engine is provided at its upper surface with the crank angle detecting sensor, the boss for mounting the sensor is disposed to be deviated sideways from the center line of the cylinder of the engine, and the sensor is mounted to the boss upside down. Therefore, the sensor does not interfere with the cooling water passage formed around the cylinder.
Further, the engine includes the starter motor, the boss for mounting the starter motor is formed on the engine, and the boss for mounting the motor is provided with another boss for mounting the other sensor. Therefore, the weight of the engine unit is reduced and the supporting rigidity thereof can be ensured sufficiently.
Furthermore, the engine includes the cam shaft driving mechanism, and the camshaft driving mechanism is disposed at a position lower than the bearing which supports the upper end of the crankshaft. Therefore, the distance between the flywheel and the bearing can be shortened.
The nature and further features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.